1. Field of the Invention
The invention relates to the improvement of art which protects a tire of a vehicle from deforming abnormally while the vehicle is running.
2. Description of the Related Art
While a vehicle is running, there is a possibility that a tire of the vehicle will deform abnormally. This abnormal deformation could be due to not only the state of the tire itself (e.g., air pressure in the tire), but may also be due to the running state of the vehicle (including the rotating state of the tire, the driving environment of the vehicle, and the like).
Therefore, it is desirable to monitor the tire of the vehicle while running. Further, it is also desirable to prevent the tire from deforming abnormally while the vehicle is running.
JPA 6-211012 discloses one example of art proposed to fulfill these kinds of needs. This related art predicts that a tire will deform abnormally based on the air pressure and temperature of the tire, and then prevents the tire from abnormally deforming by automatically decelerating the vehicle when it has been predicted that abnormal deformation will occur.
The inventor has conducted a simulation test in which the phenomenon occurring in the tire while the vehicle is running was reproduced. This test was carried out on a plurality of tires, each having different characteristics. During the test, the temperature of each tire was successively measured.
From the test, the inventor was able to see a trend in which abnormal deformation of the tire only occurred when the temperature of the tire was above a predetermined value. Based on that knowledge, the inventor learned that controlling the temperature of the tire is important for preventing abnormal deformation of the tire.
During running of the vehicle, the tire is both heated and cooled simultaneously. That is, the tire is heated by repeatedly deforming, as well as by the air outside of the vehicle, and the like. On the other hand, the tire is cooled by the flow of air moving around the tire as the vehicle runs, and the like. The tire temperature is therefore determined by the balance of these heating and cooling effects, i.e., the heat balance. On the other hand, the cooling effect of the tire from wind while the vehicle is running increases as the vehicle speed increases.
With respect to this, the foregoing related art focuses on the relationship between the tire load and the abnormal deformation, in which the tendency for abnormal tire deformation to decrease as the tire load is reduced increases, and reduces the tire load by automatically decelerating the vehicle when there is a possibility of abnormal tire deformation occurring.
As is evident from the above description, however, decelerating the vehicle reduces the cooling effect on the tire from the wind while the vehicle is running.
Therefore, based on the knowledge that it is important to control the temperature of the tire in order to prevent the tire from abnormally deforming, as mentioned above, it is important to monitor the state of the tire in terms of at least the tire temperature and/or a change in that temperature when there is a possibility of abnormal tire deformation occurring.